1. Field of the Invention
The present invention relates to a steering force controller for a power steering device, and more particularly to a steering force controller for electronic control of the steering force of an automobile dependent on input signals representing an automobile speed and the like.
2. Description of the Prior Art
There is known an automobile power steering device capable of controlling the assisting action of a power cylinder in response to input signals indicative of an automobile speed and the like. The known power steering device effects optimum steering force control by allowing the steering wheel to be operated with a smaller force in a low speed range and requiring the steering wheel to be operated with a larger force in a high speed range.
The conventional power steering device controls the assisting force of the power cylinder according to a predetermined control pattern. Where the control pattern matches a high-speed running mode of an automobile, for example, it is not suitable for use in a running mode in a geographically mountainous area or on streets. Therefore, the prior power steering device fails to control the steering force in a manner to match every actual driving mode of the automobile, giving the driver a feel of unbalanced steering power control.
To solve the above problem, a device has been developed which select different assisting forces from a power cylinder to meet the driver's preference or a particular road condition. Since this device has to be manually operated to select a desired assisting force, the driver is required to act on the device each time he judges the road condition. It is therefore tedious and time-consuming to operate the device, or the device may be operated in error or may not be operated by oversight with no desired assisting force produced.